With the rapid development of the semiconductor technology, carrier mobility enhancement technologies have attracted extensive research and applications. The drive current of a semiconductor device may be increased by increasing the carrier mobility of the channel region of the semiconductor device; and the performance of the semiconductor device may be improved.
In the fabrication of semiconductor devices, a stress may change the band gap and the carrier mobility of silicon, thus it has become more and more common to improve the performance of semiconductor devices by using the stress. Specifically, by properly controlling the stress applied onto the semiconductor devices, the carrier mobility of the channel regions of the semiconductor devices may be increased. Thus, the drive current of the semiconductor devices may be increased; and the performance of the semiconductor devices may be significantly improved. The carriers in the NMOS devices are electrons; and carriers in the PMOS devices are holes.
Currently, the embedded SiGe technology is often used to apply a compressive stress to the channel region of a PMOS device to improve the performance of the PMOS device. Specifically, a SiGe material is formed in the regions for forming the source/drain regions; and followed by doping the SiGe material to form the source/drain regions. The lattice mismatch between the silicon substrate and the SiGe material can generate a compressive stress to the channel region; the performance of the PMOS device can be improved.
Similarly, the embedded SiC technology is often used to apply a tensile stress to the channel region of an NMOS device to improve the performance of the NMOS device. Specifically, a SiC material is formed in the regions for forming the source/drain regions; and followed by doping the SiC material to form the source/drain regions. The lattice mismatch between the silicon substrate and the SiC material can generate a tensile stress to the channel region; the performance of the NMOS device can be improved.
Theoretically, the embedded SiGe technology and the embedded SiC technology may increase the carrier mobility of the semiconductor devices. However, in practical applications, it has been found that the semiconductor device with such technology may still have some issues, such as unacceptable electrical properties, etc. The disclosed device structures and methods are directed to solve one or more problems set forth above and other problems.